The present invention relates to a method and apparatus for sorting particles. More specifically, the present invention relates to a method and apparatus for sorting particles using electric and magnetic forces where the particles are electrically charged by friction and by capacitive contact.
The present invention is directed to the separation of magnetically similar particles which otherwise have dissimilar surface electric characteristics. An example of commercial significance is the separation of unburned carbon from fossil-fuel-combustion fly ash. Pulverized coal fly ash with a mean particle size of about 10 to 30 microns is collected dry by electrostatic precipitators to prevent emission to the atmosphere. The fly ash is primarily composed of cenospheres of aluminum-, silicon-, and ferruginous-oxides which tend to be strongly magnetic with apparent paramagnetic susceptibilities of the order of 100 to 10,000*10xe2x88x926 cm3/g. The cenospheres are pozzolans and have significant value as extenders for portland cement in construction applications. When diluted with a few percent by weight of unburned carbon, however, they are virtually worthless and must be disposed. The unburned carbon, called Loss On Ignition, LOI, is increasing at fossil-fuel-fired power plants because of the advent of new burner technology designed to lower emissions of nitrogen oxides, NOx. The carbon chards remaining after combustion can incorporate significant amounts of the cenospheres so carbon/cenosphere composites with varying levels of magnetism are contained in the fly ash. Because of this, attempts to separate unburned carbon from pulverized coal fly ash using magnetic separation technology have had only limited success due to the distribution of magnetism in the carbon component.
Another area that the present invention is directed to is the separation of particles which have similar surface electrical characteristics but, otherwise, have differing magnetic properties. An example is paramagnetic and diamagnetic minerals found in coal. These minerals are all undesirable because they dilute the heat content of coal and result in slagging and fouling in coal combustion. While these minerals are of distinctly differing magnetism, they generally exhibit the same triboelectric charge which is negative. Another example is the separation of nanosized magnetic particles, such as magnetite, prepared by carbon plasma arc deposition. In the arc method, some particles are created which are smaller than the critical size for formation of magnetic domains. When the particle diameter is below nominally 500*10xe2x88x928 centimeters, the critical domain size for magnetite, they do not exhibit typical properties of ferromagnets. Subdomain sized magnetite particles are superparamagnetic. They are characterized by a magnetic susceptibility and do not exhibit a locked in magnetic moment or hysteresis.
Ferromagnetic magnetite particles are used as magnetic media for information storage. Fine particle size offers the potential for greater storage density. Superparamagnetic particles also offer new methods for information storage not now used in this industry. Currently, however, the separation of subdomain sized particles from the carbon arc product is limited by the electrostatic size classification method employed. The electrostatic technology cannot be scaled to commercial throughput which limits the potential for using nanosized magnetic particles to the laboratory.
The present invention pertains to an apparatus for sorting particles. The apparatus comprises a magnet mechanism for separating the particles with a magnetic force. The apparatus comprises an electric mechanism for separating particles with an electrical force disposed adjacent to the magnet mechanism. The apparatus comprises a mechanism for providing the particles to the magnet mechanism and the electric mechanism. The providing mechanism is engaged with the magnet mechanism and the electric mechanism.
The present invention pertains to a method for sorting particles. The method comprises the steps of providing the particles to a magnet mechanism and electric mechanism disposed adjacent to the magnet mechanism. Then there is the step of separating the particles with the magnetic force from the magnet mechanism and the electric force from the electric mechanism.
The present invention pertains to an apparatus for sorting material having paramagnetic material and diamagnetic material. The apparatus comprises a region for introducing triboelectric charge to the paramagnetic material and the diamagnetic material. The apparatus comprises a magnetic region having stronger magnetic fields and weaker magnetic fields that cause paramagnetic material to move to the stronger magnetic fields and diamagnetic material to move to the weaker magnetic fields. The apparatus comprises an electric region overlapping with the magnetic region having an electric field which causes positively charged diamagnetic material to move in a first direction and negatively charged diamagnetic material to move in a second direction different from the first direction. The magnetic region and electric region are in communication with the region for introducing triboelectric charge.
The present invention pertains to a method for sorting material having paramagnetic material and diamagnetic material. The method comprises the steps of introducing triboelectric charge to the paramagnetic material and the diamagnetic material. There is the step of applying a magnetic force to the paramagnetic material and the diamagnetic material to separate the paramagnetic material from the diamagnetic material. There is the step of applying an electric force, which acts in conjunction with the magnetic force, to the diamagnetic material to separate positively charged diamagnetic material from negatively charged diamagnetic material.